[Bug c/32166] New: Condition check for const char string fails

[Bug c/32166] New: Condition check for const char string fails

[kmanjunat at gmail dot com]

Ive been working on a c program that does the error 
condition check in the beginning as follows,

char *fun(str)
const char *str;
{
  if (str == NULL) <-- Error check, taking the const char variable directly.
    printf("Null string \n");
  ..............
}

But the code fails to perform the error checking
when a NULL string is passed and gives a segmentation
fault.

Did anyone face a similar problem. Please provide me some
information regarding this problem.


-- 
           Summary: Condition check for const char string fails
           Product: gcc
           Version: 3.0
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: kmanjunat at gmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32166

[Bug c/32166] Condition check for const char string fails

[pinskia at gcc dot gnu dot org]

------- Comment #1 from pinskia at gcc dot gnu dot org  2007-05-31 16:35 -------
without a testcase it is hard to help you.
The char pointer might just point to some random memory which you might get a
crash.
Either hand us a testcase or use a debuger to debug your code more.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|major                       |normal
             Status|UNCONFIRMED                 |WAITING


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32166

[Bug c/32166] Condition check for const char string fails

[kmanjunat at gmail dot com]

------- Comment #2 from kmanjunat at gmail dot com  2007-06-01 07:52 -------
The test case is being called from a shared library with the
eabi support using dlopen.

The following is the test case

#include <stdio.h>
#include <string.h>
#include <malloc.h>


int main()
{
char *a=NULL;
char *b="abcd";
char *ret=NULL;

    ret=fun(a);
    printf("%s \n", ret);

    ret=fun(b);
    printf("%s \n", ret);

return 0;
}

Definition of fun() is in the shared library
as follows :

char *fun(str)
const char *str;
{
 int len;
 char *copy;

 if (str == NULL)
 {
   printf("Error, Null string passed \n");
   return(NULL);
 }

 len = strlen(str) + 1;

 if(!(copy = malloc(len)))
    return(NULL);

 memcpy(copy, str, len);

 return(copy);
}

The control is not getting into the condition check 
"if(str == NULL)". Ive verified this with the objdump of the 
testcase, which does not show the "cmp instruction"
for the if (str == NULL) condition checking.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32166

[Bug c/32166] Condition check for const char string fails

[rguenth at gcc dot gnu dot org]

------- Comment #4 from rguenth at gcc dot gnu dot org  2007-06-01 11:19 -------
*** Bug 32174 has been marked as a duplicate of this bug. ***


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32166

[Bug c/32166] Condition check for const char string fails

[rguenth at gcc dot gnu dot org]

------- Comment #3 from rguenth at gcc dot gnu dot org  2007-06-01 11:19 -------
*** Bug 32175 has been marked as a duplicate of this bug. ***


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32166

[Bug c/32166] Condition check for const char string fails

[pinskia at gcc dot gnu dot org]

------- Comment #5 from pinskia at gcc dot gnu dot org  2007-06-10 02:10 -------
What target are you targetting?
Also I can't reproduce this on the trunk.
Can you provide the output of "gcc -v" ?


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32166

[Bug c/32166] Condition check for const char string fails

[pinskia at gcc dot gnu dot org]

------- Comment #6 from pinskia at gcc dot gnu dot org  2007-12-02 21:32 -------
No feedback in over 3 months so closing as worksforme.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |RESOLVED
         Resolution|                            |WORKSFORME


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32166